We plan to study 20 IDDM patients age 8-30 years. If blood glucose is 150-350 mg/dl on the morning of the study, the usual insulin dose will be given except that Humalog (lispro insulin) will be used instead of regular insulin. Breakfast will be served when blood glucose is <100 mg/dl or at 90 minutes after injection, which ever comes first. The overall purpose of this study is to develop better recommendations for managing IDDM when using lispro insulin.